Image processing techniques for comparing images can have many practical applications. For example, image comparison techniques that compare an input, or test, image to one or more reference images can be applied to the detection and identification of advertisements in printed and/or broadcast media, the recognition of products in printed media and/or on store shelves, the verification of product placements in television programming, etc. A challenge faced by image comparison techniques is to reliably identify matching images in the presence of image distortion.